import { onMounted, ref, onBeforeUnmount } from 'vue'
export function scrollTopShow () {
  const scrollTopVal = ref(0)
  function scrollEvent () {
    scrollTopVal.value =
      document.documentElement.scrollTop ||
      document.body.scrollTop ||
      window.pageYOffset
  }
  onMounted(() => {
    window.addEventListener('scroll', scrollEvent)
  })
  onBeforeUnmount(() => {
    window.removeEventListener('scroll', scrollEvent)
  })
  return scrollTopVal
}
